The efficiency of pneumatic or fluidic conveying systems for particulate or other fungible materials such as grains or pellets of various material has long been recognized.
One problem with such systems is that when a change of direction is effected, the material conveyed in the system tends to continue to travel in a straight line. The result is substantial wear of the wall of the elbow, pipe or conveying member which is being used to create the change in direction.
Other problems associated with changing directions of pneumatic conveying systems include substantial pressure loss or drop in the area of the curve or radius of the turn and breakage or degradation of the product being handled by the system.
There are many and various methods and devices for addressing these problems in the prior art. U.S. Pat. Nos. 4,641,864 and 4,767,243 disclose pipe bends or elbows which cause the conveyed material to form a cushion of that material to prevent erosion of the walls of the conveying system. Similarly, there are commercially available corner fittings which cause conveyed material to impinge against material already trapped in the elbow or fitting rather than against the fitting wall, thereby reducing wear and lessening degradation of material.
U.S. Pat. Nos. 4,621,953; 3,450,442; 4,554,721; 3,144,276 and 4,595,319 disclose other methods directed to reducing erosion of the conduit forming pneumatic conveying systems. The disclosed methods include providing an impingement plate U.S. Pat. No. ('319), providing anti-erosion protrusions U.S. Pat. No. ('953) or providing wear resistant linings or materials for the inside walls of the conveying system pipe U.S. Pat. No. (721).
U.S. Pat. No. 4,387,914 discloses an elbow having an enlarged vortex chamber aligned with the entry axis to collect material and to form a vortex within the chamber thereby preventing conveyed material from hitting the walls of the elbow by causing it to deflect off the soft plug of material already collected in the chamber.
U.S. Pat. No. 3,405,738 discloses a pneumatic conveying pipe which transports material into a collector wherein the transport path is curved and the cross-sectional area of the curve is enlarged gradually from the initial bend to the final bend. This patent is directed to preventing bottlenecks in the bent portion of the transport pipe and to maintaining the passage of air flow so that powder or grains transported in the pipe will not plug the pipe.